The disclosure of Japanese Patent Application No. 11-370507 filed on Dec. 27, 1999, including the specification, drawings and abstract is incorporated herein by reference in its entirety.
1. Field of the Invention
The invention relates to brake fluid pressure control devices including a plurality of fluid pressure control valves that control fluid pressures in a plurality of brakes.
2. Description of Related Art
Japanese Laid-Open Patent Application No. 7-277175 discloses a brake fluid pressure control device including: (1) a control device mainly composed of a computer, (2) a pump that pressurizes operating fluid by means of motive power, (3) fluid pressure control valves that operate in accordance with control signals supplied from the control device and capable of controlling fluid pressures in brakes based on a fluid pressure in the pump, (4) pump shut-off valves provided between the fluid pressure control valves and the pump and that are switched in accordance with control signals supplied from the control device between a communication state where the fluid pressure control valves communicate with the pump and a shut-off state where the fluid pressure control valves are shut off from the pump, and (5) signal lines connecting the fluid pressure control valves to the control device and signal lines connecting the pump shut-off valves to the control device.
In this brake fluid pressure control device, the fluid pressure control valves are provided on the side of front wheels and on the side of rear wheels respectively. The pump shut-off valves are provided between the front-wheel-side fluid pressure control valves and the pump, and between the rear-wheel-side fluid pressure control valves and the pump respectively. If an abnormal condition arises either on the side of the front wheels or on the side of the rear wheels, the pump shut-off valves provided on the side experiencing the abnormal condition are switched to a shut-off state in accordance with control signals from the control device. Consequently, the fluid pressure control valves are shut off from the pump, and the brakes are operated by operating fluid in a master cylinder.
However, the aforementioned publication does not disclose a fail-safe system of such a brake fluid pressure control device, for example, as a countermeasure against cases where connectors for the signal lines are disconnected or incorrectly connected (where an abnormally connected condition arises) and where electric energy cannot be supplied to the fluid pressure control valves, the pump shut-off valves and the pump.
The invention has been made in view of the aforementioned circumstances. It is an object of the invention to improve fail-safe performance during abnormal operation of an electric system and thereby enhance reliability of a brake fluid pressure control device.
In order to solve the aforementioned and/or other problems, a brake fluid pressure control device according to a first aspect of the invention includes a controller, a fluid pressure control unit that operates in accordance with a control signal supplied from the controller and having a plurality of fluid pressure control valves that control fluid pressures in a plurality of brakes for inhibiting rotations of a plurality of wheels, and a plurality of signal lines connecting the fluid pressure control valves to the controller. The signal lines are divided into a plurality of signal line groups. The signal lines of a first one of the signal line groups are connected between the controller and the fluid pressure control unit by a first connector, whereas the signal lines of a second one of the signal line groups are connected between the controller and the fluid pressure control unit by a second connector.
In the brake fluid pressure control device according to the first aspect of the invention, the signal lines connecting the controller to the fluid pressure control valves respectively are divided into signal line groups, each of which includes a separate connector between the controller and the fluid pressure control unit. The signal lines are not connected altogether by a single connector but are divided into a plurality of groups, which are respectively connected by separate connectors. Accordingly, even in the case where some of the connectors fall into an abnormally connected condition, for example, due to disconnection or inappropriate fitting, as long as the other connectors are normally connected, it is possible to supply control signals to the fluid pressure control valves via the signal lines connected by the connectors that are normally (correctly) connected. The fluid pressure control valves corresponding to the normally connected signal lines can be controlled, and fluid pressures in the brakes corresponding to those fluid pressure control valves can be controlled. Thus, if fail-safe performance during abnormal operation of the electric system (during abnormal operation of the control system) is improved, it is accordingly possible to enhance reliability of the brake fluid pressure control device.
The signal lines are divided into a plurality of signal line groups. The number of the groups is arbitrary. If the number of groups increases, the number of connectors increases. However, the number of fluid pressure control valves that become incapable of receiving control signals upon occurrence of an abnormally connected condition of one connector decreases. Therefore, it is desirable to determine the number of groups in consideration of the cost required for the connectors, the influence exerted upon emergence of an abnormally connected condition of the connectors, and the like. In general, it is adequate to divide the signal lines into two or three groups. However, it is also possible to divide them into four or more groups. The connectors may be provided on either or both of the controller and the fluid pressure control unit, or at a location between the controller and the fluid pressure control unit.
The brake fluid pressure control device operates according to the first aspect of the invention, as long as the signal lines are divided into a plurality of groups, each having its own connector. The invention is not intended to exclude the possibility of providing a plurality of controllers. It is also possible to respectively control the groups by means of separate controllers.
The brakes may respectively be provided in a front-left wheel, a front-right wheel, a rear-left wheel and/or a rear-right wheel. The brakes may be divided such that one or more signal lines connected to one or more fluid pressure control valves corresponding to the brakes respectively provided in the front-left wheel and the rear-right wheel and one or more signal lines connected to one or more fluid pressure control valves corresponding to the brakes respectively provided in the front-right wheel and the rear-left wheel belong to different signal line groups.
In such a brake fluid pressure control device, the signal lines are divided such that one or more signal lines connected to one or more fluid pressure control valves that control fluid pressures in brakes for diagonally located wheels belong to the same group. Accordingly, even in the case where one of the connectors falls into an abnormally connected condition, if the other connector is normally connected, fluid pressures in the brakes for a pair of diagonally located wheels are controlled. Because fluid pressures in the brakes for the diagonally located wheels are controlled, it is possible to inhibit a decline in braking stability of the vehicle.
Furthermore, the fluid pressure control unit may be constructed to include a connecting passage connecting at least either brake cylinders for the front-left wheel and the front-right wheel or brake cylinders for the rear-left wheel and the rear-right wheel and a communication state control valve provided in the connecting passage and switched in accordance with a control signal from the controller between a communication state where two brake cylinders communicate with each other and a shut-off state where the two brake cylinders are shut off from each other.
In such a construction, the brake cylinders for the left and right wheels on the side of at least one of the front wheels and the rear wheels can communicate with each other. Accordingly, the fluid pressure control valves corresponding to a pair of diagonally located brakes can be controlled. Also, if the brake cylinders for the left and right wheels on the side of at least one of the front wheels and the rear wheels communicate with each other, fluid pressures in the left and right brakes on the side where brake cylinders communicate with each other can be controlled in common through control of the controllable fluid pressure control valves.
For example, in the case where one of the two connectors falls into an abnormally connected condition and where the fluid pressure control valves for the front-right and rear-left wheels are controllable and the fluid pressure control valves for the front-left and rear-right wheels become uncontrollable respectively, if the left and right wheels communicate with each other on the side of the front wheels, fluid pressures in the two brakes for the front-left and front-right wheels can be controlled in common by controlling the fluid pressure control valves for the front-right wheel (and the rear-left wheel).
The brakes may respectively be provided in a front-left wheel, a front-right wheel, a rear-left wheel and/or a rear-right wheel. The brakes may be divided such that one or more signal lines connected to one or more fluid pressure control valves corresponding to the brakes respectively provided in the front-left wheel and the front-right wheel and one or more signal lines connected to one or more fluid pressure control valves corresponding to the brakes respectively provided in the rear-left wheel and the rear-right wheel belong to different signal line groups.
In such a brake fluid pressure control device, the signal lines for one or more fluid pressure control valves controlling fluid pressures in the brakes for the front-left and front-right wheels belong to the same group, and the signal lines for one or more fluid pressure control valves controlling fluid pressures in the brakes for the rear-left and rear-right wheels belong to the same group. Even if one of the two connectors falls into an abnormally connected condition, the brakes for the left and right wheels either on the side of the front wheels or on the side of the rear wheels can be controlled. Therefore, it is possible to inhibit a decline in braking stability.
Furthermore, the brake fluid pressure control device may further include a pressurizing device that pressurizes operating fluid by means of motive power, and the fluid pressure control valves may be constructed to control fluid pressures in the brakes based on a fluid pressure in the pressurizing device.
In this brake fluid pressure control device, fluid pressures in the brakes are controlled based on a fluid pressure in the pressurizing device through control of the fluid pressure control valves. Accordingly, it is possible to control fluid pressures in the brakes, for example, to a pressure different from a value determined by operation of the brake actuating member by the (vehicle) driver, and to generate fluid pressures in the brakes even if the braking operation has not been performed. For example, the pressurizing device may be a pump.
A brake fluid pressure control device according to a second aspect of the invention includes a controller, a plurality of operation state detectors that detect an operation state of a brake actuating member and that supply a detection signal to the controller, and a plurality of signal lines connecting the operation state detectors to the controller. Fluid pressures in a plurality of brakes are controlled based on at least one of a plurality of values detected by the operation state detectors. In the second aspect of the invention, the signal lines are divided into a plurality of signal line groups, with each group having its own connector between the controller and the operation state detector(s) of that group.
In the brake fluid pressure control device according to the second aspect of the invention, the signal lines through which detection signals are transmitted are divided into a plurality of the signal line groups, each of which has its own separate connector. Accordingly, even if some of the connectors fall into an abnormally connected condition, it is possible to supply the detection signals to the controller.
The operation state detectors may detect an operation state of the brake actuating member either directly or indirectly. For direct detection, it is possible to employ, for example, a stroke sensor that detects an operation stroke of the brake actuating member and an operation force sensor that detects an operation force applied to the brake actuating member. For indirect detection, it is possible to employ, for example, a master pressure sensor that detects a fluid pressure in a master cylinder where a fluid pressure corresponding to an operation force of the brake actuating member is generated.
In the first and second aspects of the invention, even if some of the connectors fall into an abnormally connected condition, the fluid pressure control valves can be controlled based on an operation state of the brake actuating member detected by the detectors. Fluid pressures in the brakes can be controlled to a level based on the detected operation state.
A brake fluid pressure control device according to a third aspect of the invention includes a plurality of fluid pressure control valves capable of controlling fluid pressures in a plurality of brakes that inhibit rotations of a plurality of wheels, and a power source that supplies electric energy to the fluid pressure control valves. The fluid pressure control valves are divided into a plurality of control valve groups, which are respectively connected to the power source by separate connectors.
In the third aspect of the invention, the fluid pressure control valves are divided into the control valve groups, which are respectively connected to the power source by the separate connectors. Accordingly, even if some of the connectors fall into an abnormally connected condition, electric energy can be supplied to the fluid pressure control valves connected to the other connectors so that the fluid pressure control valves can be operated. The brake fluid pressure control device according to the third aspect of the invention may include one, two or more power sources. In the case where two or more power sources are provided, they can be provided for the control valve groups respectively. However, this is not necessary.
The brake fluid pressure control device according to the first through third aspects can be divided such that the fluid pressure control valves provided in diagonally located wheels belong to the same group. Also, if the signal lines are divided and combined with the brake fluid pressure control valves respectively connected by a plurality of connectors, an additional advantage is derived from the invention.
Furthermore, the invention can also be applied to a connector that connects a plurality of detectors to a power source.
A brake fluid pressure control device according to a fourth aspect of the invention includes a fluid pressure control unit operated by electric energy and having a plurality of fluid pressure control valves that control fluid pressures in a plurality of brakes that inhibit rotations of a plurality of wheels, and an electric energy supply device including a plurality of power sources and that supplies electric energy to the fluid pressure control valves. In the fourth aspect of the invention, the fluid pressure control valves are divided into a plurality of control valve groups, and the electric energy supply device supplies electric energy from different power sources respectively for the control valve groups.
In the brake fluid pressure control device according to the fourth aspect of the invention, a plurality of fluid pressure control valves are divided into a plurality of control valve groups, which are respectively connected to the different power sources. Therefore, even if some of the power sources fall into an abnormal condition, electric energy can be supplied from the normal (correctly functioning) power sources to the fluid pressure control valves belonging to the control valve groups connected to those power sources, so that the fluid pressure control valves can be operated. In the fourth aspect of the invention, the drive system is divided into a plurality of systems.
The power sources may or may not include generators. Also, the power sources may or may not include accumulators such as batteries.
A brake fluid pressure control device according to a fifth aspect of the invention includes a fluid pressure control unit operated by electric energy and having a plurality of fluid pressure control valves that control fluid pressures in a plurality of brakes that inhibit rotations of a plurality of wheels, and an electric energy supply device including a plurality of power sources that supply electric energy to the fluid pressure control valves. In the brake fluid pressure control device according to the fifth aspect of the invention, the electric energy supply device supplies electric energy to at least one of the fluid pressure control valves from a plurality of power sources.
In the case where the fluid pressure control valves are connected to a plurality of power sources, even if some of the power sources fall into an abnormal condition, electric energy is supplied from the other power sources. Therefore, the fluid pressure control valves can be operated. Each of the power sources connected to one fluid pressure control valve may be provided either exclusively for the brake fluid pressure control device or in common with an engine control device and the like. As long as the brake fluid pressure control device can also operate during control by the engine control device, no trouble is caused. In other words, in the case where the power sources provided in common with the engine control device fall into an abnormal condition so that no more electric energy is supplied to the engine control device, the necessity to control fluid pressures in the brakes is not urgent. Therefore, even if no electric energy is supplied to the brake fluid pressure control device, no trouble is caused. Rated voltages of the power sources may be different from one another or identical to one another.
In the case where a plurality of power sources are connected to one fluid pressure control valve, electric energy may be supplied either simultaneously from the power sources or selectively from one of the power sources. In the case where electric energy is supplied selectively from one of the power sources, it is assumed that one of the power sources serves as a primary power source and that the other power sources serve as secondary power sources. In this case, although electric energy is normally supplied from the primary power source, it is supplied from the secondary power sources upon emergence of an abnormal condition in the primary power source. In some cases, one of the power sources is selected such that electric energy is regularly supplied every time braking operation is performed or every time a set period elapses.
The power sources may have different rated voltages.
At least one of the power sources may be a battery, and a battery state detector that detects a state of the battery may be provided. The state of the battery includes a charge amount, a degree of deterioration and the like. For example, a charge amount of the battery can be detected based on at least one of an output voltage of the battery and an accumulated value of amounts of current at the time of charge and discharge. The output voltage decreases with decreases in charge amount, and there is usually a certain relation between charge amounts and output voltages. A charge amount of the battery can be obtained based on an amount of current at the time of charge and an amount of current at the time of discharge.
A degree of deterioration can be detected based on an internal resistance and a temperature. For example, if the output voltage changes greatly with respect to an output current, the internal resistance is great. If the temperature becomes higher, the internal resistance apparently becomes smaller. Accordingly, if the internal resistance remains the same, it is possible to conclude that a high degree of deterioration results from a high temperature. A degree of deterioration can be detected based on an internal resistance and a temperature.
The type of the battery is not specifically limited. For example, it is possible to employ a lead battery, a nickel/hydrogen battery, a lithium ion battery and the like.
Each of the fluid pressure control valves may include a solenoid having a coil and a movable portion operated in accordance with a state of supply of electric energy to the coil, and the at least one solenoid of the fluid pressure control valves may have a plurality of coils connected to power lines of the power sources.
In such fluid pressure control valves, the solenoid includes the coils connected to the different power sources. Thus, even if some of the power sources fall into an abnormal condition, it is possible to operate the movable portion and the fluid pressure control valves. It is possible to improve fail-safe performance during abnormal operation of the electric system and enhance reliability of the brake fluid pressure control device.
A plurality of coils are formed by winding lead wires connected to a plurality of power sources. The coils may be arranged either in series or in parallel. The coils may be provided either separately or integrally. In some cases, a plurality of lead wires are integrally wound to form a coil.
Furthermore, the brake fluid pressure control device may further include a pump device having a pump pressurizing and discharging operating fluid and a pump motor driving a pump by means of a driving force generated by electric energy. The fluid pressure control valves may be constructed to control fluid pressures in the brakes based on a fluid pressure in the pump device. The electric energy supply device may be constructed to supply electric energy to the pump motor independently from a plurality of power sources.
In such a brake fluid pressure control device, even if some of the power sources fall into an abnormal condition, the pump motor can be operated.
Furthermore, the pump motor may include a coil disposed in at least one of a stator and a rotor, and the pump motor may drive the pump by means of a driving force generated by supplying electric energy to the coil, and the at least one coil may be composed of a plurality of coil members connected to power lines of the power sources.
The type of the pump motor is not specifically limited. In many cases, however, a DC motor is used to drive the pump.
A brake fluid pressure control device according to a sixth aspect of the invention includes a plurality of operation state detectors that detect an operation state of a brake actuating member and become capable of detection through supply of electric energy, and an electric energy supply device including two or more power sources that supply electric energy to the operation state detectors. Fluid pressures in a plurality of brakes are controlled based on at least one of a plurality of values detected by the operation state detectors. The operation state detectors are divided into a plurality of detector groups, and the electric energy supply device supplies electric energy to the detector groups independently from different power sources.
In the brake fluid pressure control device according to the sixth aspect of the invention, electric energy is supplied to the detector groups independently from the different power sources. Thus, even if some of the power sources fall into an abnormal condition, electric energy can be supplied to the detectors connected to the power sources that operate normally.
Thus, these detectors are capable of detection.
It is also possible to connect a plurality of power sources to a single detector.
In the first through sixth aspects of the invention, the fluid pressure control valves may be control valves that control fluid pressures in the brakes based on a fluid pressure in a pump that includes a pump pressurizing operating fluid and a pump motor operating the pump by means of a driving force generated by electric energy. The operation state detectors may include a fluid pressure detector that detects a fluid pressure in a fluid pressure source, which generates a fluid pressure corresponding to an operation force of the brake actuating member. The controller may output a control signal to the fluid pressure control valves based on a fluid pressure detected by the fluid pressure detector.
The fluid pressure source includes a master cylinder that generates fluid pressures by means of an operation force of the brake actuating member. In addition to the master cylinder, the fluid pressure source may also include a booster device that boosts a brake operating force and transmits the boosted brake operating force to the master cylinder, and a pressure-increasing device that increases a fluid pressure in the master cylinder. If the fluid pressure source includes a booster device or a pressure-increasing device, a fluid pressure corresponding to a brake operating force and higher than a fluid pressure caused by the operation force can be generated.
Furthermore, it is possible to employ a construction in which the brakes include front-wheel-side brakes and rear-wheel-side brakes, and in which the pump device and the fluid pressure source are connected to brake cylinders for the front-wheel-side brakes, the fluid pressure source is not connected to brake cylinders for the rear-wheel-side brakes, and the pump device is connected to the brake cylinders for the rear-wheel-side brakes.
A switching device that communicates between the front-wheel-side brake cylinder and the pump device is disposed therebetween, and a switching device that communicates between the front-wheel-side brake cylinder and the fluid pressure source is disposed therebetween. On the other hand, since the pump device is always connected to the rear-wheel-side brake cylinders, there is no need to provide switching devices.
Furthermore, the fluid pressure control valve may include a pressure-increasing control valve provided between a brake cylinder of a brake and the pump device and a pressure-reducing control valve provided between the brake cylinder and a low-pressure source. The pressure-reducing control valve provided on the side of the front wheels is normally closed, and the pressure-reducing control valve provided on the side of the r ear wheels is normally opened.
Because the fluid pressure source is not connected to the rear-wheel-side brake cylinders, it is necessary to return operating fluid in the brake cylinders to the low-pressure source, for example, by keeping the pressure-decreasing control valves open for a set period in the case of cancellation of braking operation. However, if it is impossible to return all the operating fluid in the brake cylinders to the low-pressure source, the occurrence of dragging is likely. In order to avoid this, it is desirable to design the pressure-reducing control valves as normally open valves. On the other hand, the fluid pressure source is connected to the front-wheel-side brake cylinders. Thus, if the brake cylinders are in communication with the fluid pressure source, it is possible to return operating fluid in the brake cylinders to the fluid pressure source upon cancellation of braking operation.
In the case where the pressure-reducing control valves are normally open, they need to be closed immediately upon emergence of the necessity to operate the brakes. If they are closed with delay, an undesirable lag in braking effect is caused. In this case, a braking force generated on the side of the rear wheels is smaller than a braking force generated on the side of the front wheels. A lag in braking effect on the side of the rear wheels has less impact on the vehicle than it does on the side of the front wheels.
In view of the aforementioned circumstances, a technique in which brake cylinders are connected only to a pump device and pressure-reducing control valves are normally open can more suitably be put into practice on the side of the rear wheels than on the side of the front wheels.
A technique in which rear-wheel-side pressure-reducing control valves are normally open can be applied not only to the aforementioned brake control devices but also to brake control devices of other types. For example, it is applicable to a brake fluid pressure control device in which a fluid pressure source is also connected to brake cylinders for rear wheels.